harbour-core/doc/en/objfunc.txt

/*
 * Copyright 1999-2000 Chen Kedem <niki@actcom.co.il>
 *    Documentation for: __objHasData(), __objHasMethod(), __objGetMsgList(),
 *                       __objGetMethodList(), __objGetValueList(),
 *                       __objSetValueList(), __objAddMethod(),
 *                       __objAddInline(), __objAddData(), __objModMethod(),
 *                       __objModInline(), __objDelMethod(), __objDelInline(),
 *                       __objDelData(), __objDerivedFrom()
 *
 * See COPYING.txt for licensing terms.
 *
 */

/* $DOC$
   $TEMPLATE$
      Function
   $NAME$
      __objHasData()
   $CATEGORY$
      API
   $SUBCATEGORY$
      Objects
   $ONELINER$
      Determine whether a symbol exist in object as VAR
   $SYNTAX$
      __objHasData( <oObject>, <cSymbol> ) --> lExist
   $ARGUMENTS$
      <oObject> is an object to scan.

      <cSymbol> is the name of the symbol to look for.
   $RETURNS$
      __objHasData() return .T. if the given <cSymbol> exist as VAR
      (instance variable) in object <oObject), .F. if it does not exist.
   $DESCRIPTION$
      __objHasData() is a low level class support function that let you
      find out if a symbol is an instance variable in a given object.
   $EXAMPLES$
      oB := TBrowseNew( 0, 0, 24, 79 )
      ? __objHasData( oB, "nLeft" )      // this should return .T.
      ? __objHasData( oB, "lBugFree" )   // hopefully this should be .F.
      ? __objHasData( oB, "Left" )       // .F. since this is a METHOD
   $STATUS$
      R
   $COMPLIANCE$
      H
   $FILES$
      Library is core
   $SEEALSO$
      __objGetMethodList(), __objGetMsgList(), __objHasMethod()
   $END$
 */

/* $DOC$
   $TEMPLATE$
      Function
   $NAME$
      __objHasMethod()
   $CATEGORY$
      API
   $SUBCATEGORY$
      Objects
   $ONELINER$
      Determine whether a symbol exist in object as METHOD
   $SYNTAX$
      __objHasMethod( <oObject>, <cSymbol> ) --> lExist
   $ARGUMENTS$
      <oObject> is an object to scan.

      <cSymbol> is the name of the symbol to look for.
   $RETURNS$
      __objHasMethod() return .T. if the given <cSymbol> exist as METHOD
      (class function) in object <oObject), .F. if it does not exist.
   $DESCRIPTION$
      __objHasMethod() is a low level class support function that let you
      find out if a symbol is a class function in a given object.
   $EXAMPLES$
      oB := TBrowseNew( 0, 0, 24, 79 )
      ? __objHasMethod( oB, "nLeft" )      // .F. since this is a VAR
      ? __objHasMethod( oB, "FixBugs" )    // hopefully this should be .F.
      ? __objHasMethod( oB, "Left" )       // this should return .T.
   $STATUS$
      R
   $COMPLIANCE$
      H
   $FILES$
      Library is core
   $SEEALSO$
      __objGetMethodList(), __objGetMsgList(), __objHasData()
   $END$
 */

/* $DOC$
   $TEMPLATE$
      Function
   $NAME$
      __objGetMsgList()
   $CATEGORY$
      API
   $SUBCATEGORY$
      Objects
   $ONELINER$
      Return names of all VAR or METHOD for a given object
   $SYNTAX$
      __objGetMsgList( <oObject>, [<lData>], [nClassType] ) --> aNames
   $ARGUMENTS$
      <oObject> is an object to scan.

      <lData> is an optional logical value that specifies the information
      to return. A value of .T. instruct the function to return list of
      all VAR names, .F. return list of all METHOD names. Default value
      is .T.

      <nClassType> is on optional numeric code for selecting which class
      type to return. Default value is HB_MSGLISTALL, returning the whole
      list.
   $RETURNS$
      __objGetMsgList() return an array of character stings with all VAR
      names or all METHOD names for a given object. __objGetMsgList()
      would return an empty array {} if the given object does not contain
      the requested information.
   $DESCRIPTION$
      __objGetMsgList() is a low level class support function that let you
      find all instance variable or method names for a given object.

      If specified, the following table shows the values for <nClassType>
      that allow you to distinguish between VAR and CLASS VAR:

      table>
      hboo.ch           Meaning

      HB_MSGLISTALL     All types
      HB_MSGLISTCLASS   CLASS VAR only
      HB_MSGLISTPURE    VAR only
      /table>

      VAR are instance variable usable within each object from a class,
      where each object has its own VARs.

      CLASS VAR are shared by all objects from a Class, so the changed
      value within Object1 will be reflected when accessing the CLASS VAR
      from Object2.
   $EXAMPLES$
      // show information about TBrowse class
      oB := TBrowseNew( 0, 0, 24, 79 )
      aData      := __objGetMsgList( oB, .T. )
      aClassData := __objGetMsgList( oB, .T., HB_MSGLISTCLASS )
      aMethod    := __objGetMsgList( oB, .F. )
      FOR EACH x IN aData
         ? "VAR name:", x
      NEXT
      FOR EACH x IN aClassData
         ? "CLASS VAR name:", x
      NEXT
      FOR EACH x IN aMethod
         ? "METHOD name:", x
      NEXT
   $STATUS$
      R
   $COMPLIANCE$
      H
   $FILES$
      Header file is hboo.ch
      Library is core
   $SEEALSO$
      __objGetMethodList(), __objGetValueList(), __objHasData(), __objHasMethod()
   $END$
 */

/* $DOC$
   $TEMPLATE$
      Function
   $NAME$
      __objGetMethodList()
   $CATEGORY$
      API
   $SUBCATEGORY$
      Objects
   $ONELINER$
      Return names of all METHOD for a given object
   $SYNTAX$
      __objGetMethodList( <oObject> ) --> aMethodNames
   $ARGUMENTS$
      <oObject> is an object to scan.
   $RETURNS$
      __objGetMethodList() return an array of character stings with all
      METHOD names for a given object. __objGetMethodList() would return
      an empty array {} if the given object does not contain any METHOD.
   $DESCRIPTION$
      __objGetMethodList() is a low level class support function that let
      you find all class functions names for a given object.
      It is equivalent to __objGetMsgList( oObject, .F. ).
   $EXAMPLES$
      // show information about TBrowse class
      oB := TBrowseNew( 0, 0, 24, 79 )
      FOR EACH s IN __objGetMethodList( oB )
         ? "METHOD name:", s
      NEXT
   $STATUS$
      R
   $COMPLIANCE$
      H
   $FILES$
      Library is core
   $SEEALSO$
      __objGetMsgList(), __objGetValueList(), __objHasData(), __objHasMethod()
   $END$
 */

/* $DOC$
   $TEMPLATE$
      Function
   $NAME$
      __objGetValueList()
   $CATEGORY$
      API
   $SUBCATEGORY$
      Objects
   $ONELINER$
      Return an array of VAR names and values for a given object
   $SYNTAX$
      __objGetValueList( <oObject>, [<aExcept>] ) --> aData
   $ARGUMENTS$
      <oObject> is an object to scan.

      <aExcept> is an optional array with VAR names you want to exclude
      from the scan.
   $RETURNS$
      __objGetValueList() return a 2D array that contain pairs of a VAR
      symbol name and the value of VAR. __objGetValueList() would return
      an empty array {} if the given object does not contain the requested
      information.
   $DESCRIPTION$
      __objGetValueList() is a low level class support function that
      return an array with VAR names and value, each array element is a
      pair of: aData[ i, HB_OO_DATA_SYMBOL ] contain the symbol name
               aData[ i, HB_OO_DATA_VALUE  ] contain the value of DATA
   $EXAMPLES$
      // show information about TBrowse class
      oB := TBrowseNew( 0, 0, 24, 79 )
      FOR EACH i IN __objGetValueList( oB )
         ? ;
           "VAR name:", i[ HB_OO_DATA_SYMBOL ], ;
           "   value=", i[ HB_OO_DATA_VALUE ]
      NEXT
   $STATUS$
      R
   $COMPLIANCE$
      H
   $FILES$
      Header file is hboo.ch
      Library is core
   $SEEALSO$
      __objGetMethodList(), __objGetMsgList(), __objHasData(), __objHasMethod(), __objSetValueList()
   $END$
 */

/* $DOC$
   $TEMPLATE$
      Function
   $NAME$
      __objSetValueList()
   $CATEGORY$
      API
   $SUBCATEGORY$
      Objects
   $ONELINER$
      Set object with an array of VAR names and values
   $SYNTAX$
      __objSetValueList( <oObject>, <aData> ) --> oObject
   $ARGUMENTS$
      <oObject> is an object to set.

      <aData> is a 2D array with a pair of instance variables and values
      for setting those variable.
   $RETURNS$
      __objSetValueList() return a reference to <oObject>.
   $DESCRIPTION$
      __objSetValueList() is a low level class support function that let
      you set a group of instance variables with values. each array
      element in <aData> is a pair of:
      aData[ i, HB_OO_DATA_SYMBOL ] which contain the variable name to set
      aData[ i, HB_OO_DATA_VALUE  ] contain the new variable value.
   $EXAMPLES$
      // set some TBrowse instance variable
      oB := TBrowse():New()
      aData := Array( 4, 2 )
      aData[ 1, HB_OO_DATA_SYMBOL ] = "nTop"
      aData[ 1, HB_OO_DATA_VALUE  ] = 1
      aData[ 2, HB_OO_DATA_SYMBOL ] = "nLeft"
      aData[ 2, HB_OO_DATA_VALUE  ] = 10
      aData[ 3, HB_OO_DATA_SYMBOL ] = "nBottom"
      aData[ 3, HB_OO_DATA_VALUE  ] = 20
      aData[ 4, HB_OO_DATA_SYMBOL ] = "nRight"
      aData[ 4, HB_OO_DATA_VALUE  ] = 70
      __objSetValueList( oB, aData )
      ? oB:nTop      // 1
      ? oB:nLeft     // 10
      ? oB:nBottom   // 20
      ? oB:nRight    // 70
   $STATUS$
      R
   $COMPLIANCE$
      H
   $FILES$
      Header file is hboo.ch
      Library is core
   $SEEALSO$
      __objGetValueList()
   $END$
 */

/* $DOC$
   $TEMPLATE$
      Function
   $NAME$
      __objAddMethod()
   $CATEGORY$
      API
   $SUBCATEGORY$
      Objects
   $ONELINER$
      Add a METHOD to an already existing class
   $SYNTAX$
      __objAddMethod( <oObject>, <cMethodName>, <nFuncPtr> ) --> oObject
   $ARGUMENTS$
      <oObject> is the object to work on.

      <cMethodName> is the symbol name of the new METHOD to add.

      <nFuncPtr> is a pointer to a function to associate with the method.
   $RETURNS$
      __objAddMethod() return a reference to <oObject>.
   $DESCRIPTION$
      __objAddMethod() is a low level class support function that add a
      new METHOD to an object. <oObject> is unchanged if a symbol with the
      name <cMethodName> already exist in <oObject>.

      Note that <nFuncPtr> is a special pointer to a function that was
      created using the @ operator, see example below.
   $EXAMPLES$
      // create a new THappy class and add a Smile method
      oHappy := HBClass():New( "THappy" )
      __objAddMethod( oHappy, "Smile", @MySmile() )
      ? oHappy:Smile( 1 )       // :)
      ? oHappy:Smile( 2 )       // ;)
      ? oHappy:Smile( 3 )       // *SMILE*

      STATIC FUNCTION MySmile( nType )
         IF HB_ISNUMERIC( nType )
            SWITCH nType
            CASE 1 ; RETURN ":)"
            CASE 2 ; RETURN ";)"
            CASE 3 ; RETURN "*SMILE*"
            ENDSWITCH
         ENDIF
         RETURN NIL
   $STATUS$
      R
   $COMPLIANCE$
      H
   $FILES$
      Library is core
   $SEEALSO$
      __objAddInline(), __objAddData(), __objDelMethod(), __objGetMethodList(), __objGetMsgList(), __objHasMethod(), __objModMethod()
   $END$
 */

/* $DOC$
   $TEMPLATE$
      Function
   $NAME$
      __objAddInline()
   $CATEGORY$
      API
   $SUBCATEGORY$
      Objects
   $ONELINER$
      Add an INLINE to an already existing class
   $SYNTAX$
      __objAddInline( <oObject>, <cInlineName>, <bInline> ) --> oObject
   $ARGUMENTS$
      <oObject> is the object to work on.

      <cInlineName> is the symbol name of the new INLINE to add.

      <bInline> is a code block to associate with the INLINE method.
   $RETURNS$
      __objAddInline() return a reference to <oObject>.
   $DESCRIPTION$
      __objAddInline() is a low level class support function that add a
      new INLINE method to an object. <oObject> is unchanged if a symbol
      with the name <cInlineName> already exist in <oObject>.
   $EXAMPLES$
      // create a new THappy class and add a Smile INLINE method
      oHappy := HBClass():New( "THappy" )
      bInline := {| nType | { ":)", ";)", "*SMILE*" }[ nType ] }
      __objAddInline( oHappy, "Smile", bInline )
      ? oHappy:Smile( 1 )       // :)
      ? oHappy:Smile( 2 )       // ;)
      ? oHappy:Smile( 3 )       // *SMILE*
   $STATUS$
      R
   $COMPLIANCE$
      H
   $FILES$
      Library is core
   $SEEALSO$
      __objAddData(), __objAddMethod(), __objDelInline(), __objGetMethodList(), __objGetMsgList(), __objHasMethod() , __objModInline()
   $END$
 */

/* $DOC$
   $TEMPLATE$
      Function
   $NAME$
      __objAddData()
   $CATEGORY$
      API
   $SUBCATEGORY$
      Objects
   $ONELINER$
      Add a VAR to an already existing class
   $SYNTAX$
      __objAddData( <oObject>, <cDataName> ) --> oObject
   $ARGUMENTS$
      <oObject> is the object to work on.

      <cDataName> is the symbol name of the new VAR to add.
   $RETURNS$
      __objAddData() return a reference to <oObject>.
   $DESCRIPTION$
      __objAddData() is a low level class support function that add a new
      VAR to an object. <oObject> is unchanged if a symbol with the name
      <cDataName> already exist in <oObject>.
   $EXAMPLES$
      // create a new THappy class and add a lHappy VAR
      oHappy := HBClass():New( "THappy" )
      __objAddData( oHappy, "lHappy" )
      oHappy:lHappy := .T.
      IF oHappy:lHappy
         ? "Happy, Happy, Joy, Joy !!!"
      ELSE
         ? ":(..."
      ENDIF
   $STATUS$
      R
   $COMPLIANCE$
      H
   $FILES$
      Library is core
   $SEEALSO$
      __objAddInline(), __objAddMethod(), __objDelData(), __objGetMsgList(), __objGetValueList(), __objHasData(), __objSetValueList()
   $END$
 */

/* $DOC$
   $TEMPLATE$
      Function
   $NAME$
      __objModMethod()
   $CATEGORY$
      API
   $SUBCATEGORY$
      Objects
   $ONELINER$
      Modify (replace) a METHOD in an already existing class
   $SYNTAX$
      __objModMethod( <oObject>, <cMethodName>, <nFuncPtr> ) --> oObject
   $ARGUMENTS$
      <oObject> is the object to work on.

      <cMethodName> is the symbol name of the METHOD to modify.

      <nFuncPtr> is a pointer to a new function to associate with the
      method.
   $RETURNS$
      __objModMethod() return a reference to <oObject>.
   $DESCRIPTION$
      __objModMethod() is a low level class support function that modify
      a METHOD in an object and replace it with a new function. <oObject>
      is unchanged if a symbol with the name <cMethodName> does not exist
      in <oObject>. __objModMethod() is used in inheritance mechanism.

      Note that <nFuncPtr> is a special pointer to a function that was
      created using the @ operator, see example below.
   $EXAMPLES$
      // create a new THappy class and add a Smile method
      oHappy := HBClass():New( "THappy" )
      __objAddMethod( oHappy, "Smile", @MySmile() )
      ? oHappy:Smile( 1 )       // :)
      ? oHappy:Smile( 2 )       // ;)
      // replace Smile method with a new function
      __objAddMethod( oHappy, "Smile", @YourSmile() )
      ? oHappy:Smile( 1 )       // *SMILE*
      ? oHappy:Smile( 2 )       // *WINK*

      STATIC FUNCTION MySmile( nType )
         LOCAL cSmile
         DO CASE
         CASE nType == 1
            cSmile := ":)"
         CASE nType == 2
            cSmile := ";)"
         ENDCASE
         RETURN cSmile

      STATIC FUNCTION YourSmile( nType )
         LOCAL cSmile
         DO CASE
         CASE nType == 1
            cSmile := "*SMILE*"
         CASE nType == 2
            cSmile := "*WINK*"
         ENDCASE
         RETURN cSmile
   $STATUS$
      R
   $COMPLIANCE$
      H
   $FILES$
      Library is core
   $SEEALSO$
      __objAddMethod(), __objDelMethod(), __objGetMethodList(), __objGetMsgList(), __objHasMethod()
   $END$
 */

/* $DOC$
   $TEMPLATE$
      Function
   $NAME$
      __objModInline()
   $CATEGORY$
      API
   $SUBCATEGORY$
      Objects
   $ONELINER$
      Modify (replace) an INLINE method in an already existing class
   $SYNTAX$
      __objModInline( <oObject>, <cInlineName>, <bInline> ) --> oObject
   $ARGUMENTS$
      <oObject> is the object to work on.

      <cInlineName> is the symbol name of the INLINE method to modify.

      <bInline> is a new code block to associate with the INLINE method.
   $RETURNS$
      __objModInline() return a reference to <oObject>.
   $DESCRIPTION$
      __objModInline() is a low level class support function that modify
      an INLINE method in an object and replace it with a new code block.
      <oObject> is unchanged if a symbol with the name <cInlineName> does
      not exist in <oObject>. __objModInline() is used in inheritance
      mechanism.
   $EXAMPLES$
      // create a new THappy class and add a Smile INLINE method
      oHappy := HBClass():New( "THappy" )
      bMyInline   := {| nType | { ":)", ";)" }[ nType ] }
      bYourInline := {| nType | { "*SMILE*", "*WINK*" }[ nType ] }
      __objAddInline( oHappy, "Smile", bMyInline )
      ? oHappy:Smile( 1 )       // :)
      ? oHappy:Smile( 2 )       // ;)
      // replace Smile inline method with a new code block
      __objModInline( oHappy, "Smile", bYourInline )
      ? oHappy:Smile( 1 )       // *SMILE*
      ? oHappy:Smile( 2 )       // *WINK*
   $STATUS$
      R
   $COMPLIANCE$
      H
   $FILES$
      Library is core
   $SEEALSO$
      __objAddInline(), __objDelInline(), __objGetMethodList(), __objGetMsgList(), __objHasMethod()
   $END$
 */

/* $DOC$
   $TEMPLATE$
      Function
   $NAME$
      __objDelMethod()
   $CATEGORY$
      API
   $SUBCATEGORY$
      Objects
   $ONELINER$
      Delete a METHOD  from class
   $SYNTAX$
      __objDelMethod( <oObject>, <cSymbol> ) --> oObject
   $ARGUMENTS$
      <oObject> is the object to work on.

      <cSymbol> is the symbol name of METHOD or INLINE method to be
      deleted (removed) from the object.
   $RETURNS$
      __objDelMethod() return a reference to <oObject>.
   $DESCRIPTION$
      __objDelMethod() is a low level class support function that deletes
      (removes) a METHOD or an INLINE method from an object. <oObject> is
      unchanged if a symbol with the name <cSymbol> does not exist in
      <oObject>.

      __objDelInline() is exactly the same as __objDelMethod().
   $EXAMPLES$
      // create a new THappy class and add a Smile method
      oHappy := HBClass():New( "THappy" )
      __objAddMethod( oHappy, "Smile", @MySmile() )
      ? __objHasMethod( oHappy, "Smile" )    // .T.
      // remove Smile method
      __objDelMethod( oHappy, "Smile" )
      ? __objHasMethod( oHappy, "Smile" )    // .F.

      STATIC FUNCTION MySmile( nType )
         LOCAL cSmile
         DO CASE
         CASE nType == 1
            cSmile := ":)"
         CASE nType == 2
            cSmile := ";)"
         ENDCASE
         RETURN cSmile
   $STATUS$
      R
   $COMPLIANCE$
      H
   $FILES$
      Library is core
   $SEEALSO$
      __objAddInline(), __objAddMethod(), __objGetMethodList(), __objGetMsgList(), __objHasMethod(), __objModInline(), __objModMethod()
   $END$
 */

/* $DOC$
   $TEMPLATE$
      Function
   $NAME$
      __objDelInline()
   $CATEGORY$
      API
   $SUBCATEGORY$
      Objects
   $ONELINER$
      Delete a METHOD INLINE from class
   $SYNTAX$
      __objDelInline( <oObject>, <cSymbol> ) --> oObject
   $ARGUMENTS$
      <oObject> is the object to work on.

      <cSymbol> is the symbol name of METHOD or INLINE method to be
      deleted (removed) from the object.
   $RETURNS$
      __objDelInMethod() return a reference to <oObject>.
   $DESCRIPTION$
      __objDelInMethod() is a low level class support function that delete
      (remove) a METHOD or an INLINE method from an object. <oObject> is
      unchanged if a symbol with the name <cSymbol> does not exist in
      <oObject>.
   $EXAMPLES$
      // create a new THappy class and add a Smile method
      oHappy := HBClass():New( "THappy" )
      __objAddMethod( oHappy, "Smile", @MySmile() )
      ? __objHasMethod( oHappy, "Smile" )    // .T.
      // remove Smile method
      __objDelInMethod( oHappy, "Smile" )
      ? __objHasMethod( oHappy, "Smile" )    // .F.

      STATIC FUNCTION MySmile( nType )
         LOCAL cSmile
         DO CASE
         CASE nType == 1
            cSmile := ":)"
         CASE nType == 2
            cSmile := ";)"
         ENDCASE
         RETURN cSmile
   $STATUS$
      R
   $COMPLIANCE$
      H
   $FILES$
      Library is core
   $SEEALSO$
      __objAddInline(), __objAddMethod(), __objGetMethodList(), __objGetMsgList(), __objHasMethod(), __objModInline(), __objModMethod()
   $END$
 */

/* $DOC$
   $TEMPLATE$
      Function
   $NAME$
      __objDelData()
   $CATEGORY$
      API
   $SUBCATEGORY$
      Objects
   $ONELINER$
      Delete a VAR (instance variable) from class
   $SYNTAX$
      __objDelMethod( <oObject>, <cDataName> ) --> oObject
   $ARGUMENTS$
      <oObject> is the object to work on.

      <cDataName> is the symbol name of VAR to be deleted (removed) from
      the object.
   $RETURNS$
      __objDelData() return a reference to <oObject>.
   $DESCRIPTION$
      __objDelData() is a low level class support function that delete
      (remove) a VAR from an object. <oObject> is unchanged if a symbol
      with the name <cDataName> does not exist in <oObject>.
   $EXAMPLES$
      // create a new THappy class and add a lHappy VAR
      oHappy := HBClass():New( "THappy" )
      __objAddData( oHappy, "lHappy" )
      ? __objHasData( oHappy, "lHappy" )    // .T.
      // remove lHappy VAR
      __objDelData( oHappy, "lHappy" )
      ? __objHasData( oHappy, "lHappy" )    // .F.
   $STATUS$
      R
   $COMPLIANCE$
      H
   $FILES$
      Library is core
   $SEEALSO$
      __objAddData(), __objGetMsgList(), __objGetValueList(), __objHasData(), __objSetValueList()
   $END$
 */

/* $DOC$
   $TEMPLATE$
      Function
   $NAME$
      __objDerivedFrom()
   $CATEGORY$
      API
   $SUBCATEGORY$
      Objects
   $ONELINER$
      Determine whether a class is derived from another class
   $SYNTAX$
      __objDerivedFrom( <oObject>, <xSuper> ) --> lIsParent
   $ARGUMENTS$
      <oObject> is the object to check.

      <xSuper> is the object that may be a parent. <xSuper> can be either
      an Object or a Character string with the class name.
   $RETURNS$
      __objDerivedFrom() return a logical TRUE (.T.) if <oObject> is
      derived from <xSuper>.
   $DESCRIPTION$
      __objDerivedFrom() is a low level class support function that check
      is one class is a super class of the other, or in other words, does
      class <oObject> a child or descendant of <xSuper>.
   $EXAMPLES$
      // Create three classes and check their relations

      #include "hbclass.ch"
      PROCEDURE Main()
         LOCAL oSuper, oObject, oDress
         oSuper  := TMood():New()
         oObject := THappy():New()
         oDress  := TShirt():New()
         ? __objDerivedFrom( oObject, oSuper )    // .T.
         ? __objDerivedFrom( oSuper, oObject )    // .F.
         ? __objDerivedFrom( oObject, oDress )    // .F.
         RETURN

      CREATE CLASS TMood
         METHOD New() INLINE Self
      ENDCLASS

      CREATE CLASS THappy INHERIT TMood
         METHOD Smile() INLINE QOut( "*smile*" )
      ENDCLASS

      CREATE CLASS TShirt
         VAR Color
         VAR Size
         METHOD New() INLINE Self
      ENDCLASS
   $STATUS$
      R
   $COMPLIANCE$
      H
   $FILES$
      Library is core
   $SEEALSO$
      __objHasData(), __objHasMethod()
   $END$
 */